The field of the invention generally relates to clothes dryers and more particularly relates to apparatus for controlling the flow of air through clothes dryers.
In a prior art commercial clothes dryer, a burner box communicates with an inlet on the back wall of a horizontally oriented clothes drum that has a perforated front annulus. A stationary suction duct has an arcuate top mouth that conforms with and is positioned in close spaced relationship with an underside portion of the perforated annulus. Thus, even though the drum is rotated to tumble the clothes, the suction duct is always aligned with a portion of the perforated annulus such that air is continuously being drawn from the burner box through the clothes drum and into the suction duct via the perforations that are instantaneously aligned with the suction duct. The air in the suction duct passes through a filter which collects the lint, and then back a conduit to an exhaust fan which provides the induced draft for the heretofore described air flow. The air is then exhausted or, alternately, a small percentage of the air may be recirculated back into the clothes drum.
Even though the intended air flow path in the above described arrangement is from the rotating clothes drum into the suction duct through the perforations that are instantaneously aligned with the mouth of the suction duct, some lint laden air also exits perforations that are not instantaneously aligned with the suction duct. More specifically, there is a small gap between the suction duct and the outer surface of the drum, and air is drawn into the suction duct through this gap thereby creating a slightly negative pressure inside the outer cabinet of the dryer. This slightly negative pressure along with the effects of centrifugal force within the drum cause some lint laden air to exit drum perforations that are instantaneously at the top and sides (i.e. perforations that are not instantaneously aligned with the suction duct at the bottom).
The unintended air flow path through the top and side perforations causes several problems. First, this air carries lint which drops down and collects in the interior of the cabinet thereby requiring relatively frequent cleaning. Thus, the periodic maintenance costs of the dryer are relatively high. Second, this air is hot and heats the interior of the cabinet thereby decreasing the overall efficiency of the dryer. Third, the temperature in the drum becomes difficult to regulate because the burner controller senses the exhaust air temperature which does not accurately correspond to the drum temperature if there are unknown and variable heat losses from the drum to the interior of the cabinet. Thus, the drum may operate too hot if there are greater than normal heat losses to the cabinet interior, or too cool if such heat losses are less than normal.
A rigid cylindrical baffle has been connected to the outer cabinet and used to surround the perforated annulus, but such arrangement has not provided an effective seal for eliminating the above described unintended air flow path. Further, the baffle is difficult to install as part of a retrofit kit, and it is also difficult to remove and reinstall it later for maintenance and repair.